Many JS tests call stopBalancer() unnecessarily because ShardingTest does it by default now. Also check that startBalancer() is not called when it could be instead specified in the ShardingTest using the enableBalancer parameter.

This fix is important because writes to the config db do not yet support any retries, and the sharding_csrs_continuous_config_stepdown suite must blacklist tests that do not currently support command retries. Removing unnecessary writes keeps some tests in the suite.